So right now, if you set a conduit to Round Robin on extract, it pretty much makes priority settings obsolete, because it will try to input in lower priority outputs even though higher priority outputs still need items/fluids first

The way it should work is:
RR highest priority untill all of those are filled, then go down the list from there, doing the same at each priority setting

So that if let's say priority 1 uses too much items/fluids, priority 0 and below should never get any, no matter what.
1.12.2

Also take a peek at #1130 for further discussion.